Fluid distribution systems, in particular mobile fluid distribution systems, are used in a variety of applications. For example, at mining and construction sites, it is common to use mobile fluid distribution systems to spray water over routes and work areas to minimize the creation of dust during operations. A specific example might include a water truck that sprays water over roads at a mine site.
Other applications of mobile fluid distribution systems may include spraying of pesticides and herbicides, e.g., for agricultural use, disbursement of saline solutions on roads for snow and ice control, fire suppression, and the like.
For various reasons, such as cost and consistent fluid application, it is desired to maintain control of the amount and pattern of fluids being distributed, in particular with regard to maintaining a uniform and consistent application of fluid per unit of area. For example, when spraying water on mine roads, it may be desired to uniformly distribute the water over the road surface to avoid applying excess water in specific locations. In particular, it is desired to provide a spray head capable of distributing fluid in a consistently wide spray that is less dependent on flow rate or pressure. The desire is to provide consistent spray patterns in areas, such as on inclines and at intersections, where flow rates may be decreased due to decreased machine speed or the need to decrease the amount of fluid per unit area.
Typical fluid distribution systems spray fluids at flows that are directly proportional to engine speeds of the mobile machines. Operators attempt to keep the fluid flow relatively constant by maintaining constant engine speeds, at least to the extent possible. These efforts typically require operating mobile machines at reduced transmission gear ratios to maintain desired engine speeds. However, these efforts cannot be maintained, for example, when ascending or descending steep inclines, conditions which generally require changing engine speeds. The spray head's spray pattern changes as the flow changes, making it difficult for an operator to distribute the desired fluid per unit of area without causing spray overlap, often significant in nature, from multiple spray heads that causes poor traction conditions. More specifically, at low rates of speed, and the accompanying low flow rates, the spray width will typically be considerably decreased, resulting in poor consistency in coverage.
Efforts have been made to maintain fluid flow in proportion to machine speed, i.e., ground speed, rather than engine speed. Although this has resulted in improved fluid distribution per unit area, it is still difficult to maintain precise control during various operating maneuvers, such as starting and stopping, and as operating conditions vary. Furthermore, many of these systems still distribute fluids in proportion to fluid flow, which adds to the difficulty of consistent application per unit of area.
One example of an attempt to achieve uniform fluid application is described in U.S. Pat. No. 5,964,410 to Brown et al. (the Brown patent). Brown employs spray heads with variable orifices to attempt maintenance of constant velocities and exit flow trajectories. The spray heads are pressure controlled, however, relying on pressure of the fluid being sprayed to overcome a spring force to open the spray nozzle. Furthermore, the components that are used to control the nozzle are located in the main fluid flow chamber, and thus are susceptible to corrosion and contamination by particles and debris in the fluid. As a result, the system would still have difficulty achieving consistent application of the fluid per unit of area during various operating conditions.
The present disclosure is directed to overcoming one or more of the problems as set forth above.